To all who replied -

Thanks for the info. The thing is that I had the hull waxed before leaving,
and it stained anyway. Maybe the wax needs to be applied heavier ?? Also,
whatever I use to remove the stain, I don't want it to cut through the was.
I wonder if oxalic acid, On-Off, lemon juice or the toilet bowl cleaner
would leave the wax or take it off ?

GC